Molecular Genetics: DNA, RNA, and Gene Expression
From DNA to Phenotype
Central dogma
Genetic information is stored in DNA, transcribed into RNA, and translated into protein. Proteins then influence cellular structure and function, producing phenotype.
Replication and transcription
DNA replication is semiconservative: each new DNA molecule contains one original strand and one newly synthesized strand. During transcription, RNA polymerase synthesizes RNA complementary to the DNA template strand.
Regulation matters
Not all genes are expressed equally. Gene regulation lets cells specialize while sharing the same genome.
Which enzyme synthesizes RNA during transcription?
RNA polymerase catalyzes RNA synthesis using a DNA template.
Correct answer: RNA polymerase
What is the role of tRNA in translation?
tRNA acts as an adaptor between nucleic acid code and amino acid sequence.
Correct answer: It carries amino acids to the ribosome and matches anticodons with mRNA codons.
Gene expression stages
| Stage | Main event |
|---|---|
| Replication | DNA copied before division |
| Transcription | RNA made from DNA template |
| Translation | Protein made from mRNA |
| Post-translational processing | Protein modified and targeted |
A mutation that changes a DNA codon may affect the protein because it can:
A codon change can alter the amino acid incorporated during translation, potentially changing protein function.
Correct answer: Alter the amino acid sequence